This invention relates to absorbent pads fabricated of laminated layers of absorbent tissue and, more particularly, to such pads which contain theft alarm activators therein.
Absorbent pads particularly designed for packaging with meat, poultry and fish food products are used in food markets, poultry processing plants and the like to reduce product display costs and to provide a cleaner, more attractive product. These pads are generally wrapped with the food product on the underside thereof to absorb liquids which may "bleed" from the product. In poultry products, for example, it is customary to place the poultry parts of a given package in a molded shallow tray of foamed plastic or the like. One of these absorbent pads is placed in the bottom of the tray and the poultry parts are placed thereon. The complete package is then wrapped with clear polyethylene or the like.
Packaged meat products sold in retail establishments, such as meat markets and supermarkets, may have a significant monetary value. Typically, such products will have a price of several dollars or even a dollar value in double digits. This level of value is such that shoplifting begins to become a serious problem. At the same time, it begins to be worthwhile for the marketing establishment to incur the additional expense of theft detection systems in order to prevent or deter shoplifting.
Typically, such systems work with products including an alarm activator element (a "tag"), a device for deactivating the element at the point of sale, such as a checkout counter, and a sensor at a point where people exiting the establishment must pass by. In one such system, the activator element is a small strip or wire of magnetic material which is initially magnetized as a permanent magnet. In conjunction with such a system, there is a device at the checkout counter for generating a demagnetizing field. If the activator element or "tag" is not demagnetized, it activates the theft alarm when the person carrying the product passes by the sensor.
Another theft detection system, similar in concept but using a somewhat different tag and means and method for deactivating the tag, is also known in the art. This utilizes tags (alarm activator elements) based on "acoustomagnetic" principles. The system operates at a carefully chosen narrow band of low radio frequencies, for example 58 kilohertz (kHz). The selected frequencies minimize any interference from other electronics.
In this system, the tag contains a resonator made of an amorphous magnetic material of a precise length and thickness, which is excited by low-frequency radio signals generated by a transmitter at the store's entrance/exit. The resonator vibrates at the same frequency, thus transmitting an identical signal. A receiver which is also positioned at the entrance/exit detects the resonator's signal and initiates an alarm.
One of the benefits of this acoustomagnetic detection system is that the low-frequency radio signals from the transmitter can penetrate foil shielding which might be used by a would-be shoplifter to defeat other types of detector units.
One particular theft detection system, based on acoustomagnetic principles, provides a transmitter unit mounted at a pedestal adjacent a store entrance or checkout aisle. This unit transmits 58 kilohertz low-radio-frequency pulses (referred to as "blue pulses") at 11-millisecond intervals. A resonator positioned inside an absorbent pad of the present invention, when passing through the pedestal, begins to vibrate at 58 kilohertz, identical to the transmitted frequency, thereby sending "red pulses". A receiver, also installed at the pedestal, is turned on during the 11-millisecond interval between the blue pulses so that it can pick up the red pulses emitted by the tag installed in the product in response to the transmission of the blue pulses. If the receiver receives a signal at least four times, it sets off an alarm.
The tag contains a magnetized strip adjacent to the resonator which insures that the oscillations of the resonator remain precisely at 58 kilohertz. A scanning device at the checkout counter can turn off the tag when the merchandise is sold by demagnetizing the strip or by altering its magnetic properties. At that point the resonator either does not vibrate (does not emit red pulses) or it resonates at the wrong frequency so that its pulses are not recognized by the receiver.
U.S. Pat. No. 5,320,895 of Lionel M. Larsonneur and Stanley E. Schilcher discloses an absorbent pad for use with meat and poultry products in retail sale packages. The disclosure of that patent is incorporated herein by reference as though set out in haec verba. It has a laminated tissue absorbent mat sandwiched between upper and lower plastic sheets. During production of the pad, aligned channels are established through the pad from top to bottom by the penetration of a series of perforating pins.
In the case of absorbent pads having theft alarm activator elements which are used with meat and poultry products, the packaging is such that the pad is usually visible, at least in major extent, at the underside of the product within its transparent wrapping. For pads such as are known in the prior art having an alarm activator element, the element is generally readily apparent to a discerning shoplifter because it is positioned along the upper exterior surface of the pad. It would be preferable for such an absorbent pad to have its theft alarm activator element out of sight within the pad, such as between the tissue layers of an absorbent pad constructed of tissue layer laminations. Other materials suitable for the laminated layers are cellulose, airlaid and composites.